Aluminum base alloy powder product



ALUM BASE ALLOY POWDER PRODUCT Raymond J. Towner and John P. Lyle, J12,New Kensington, Pa., assignors to Aluminum Company of America,Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed Mar.27, 1958, Ser. No. 724,226

3 Claims. (Cl. 29-182) This invention relates to articles made fromaluminum base alloy powders and it is more particularly concerned withthose products resulting from heating and working a compacted mass ofatomized particles of an aluminum manganese base alloy.

Heretofore, compressed and sintered bodies of oxidecoated aluminum flakepowders have been produced p.s.i.

2,966,731 Patented Jan. 3, 1961 The aluminum-manganese powder productscan be readily worked under the usual hot working conditions oftemperature and pressure employed in fabricating conventional aluminumand aluminum base alloy articles. Furthermore, the hot-worked productcan be cold worked to a limited extent, if desired. The fabricatedaluminum alloy products can be placed in service without any preliminarythermal treatment. The strength of the wrought powder products atelevated temperatures is not influenced to any significant extent by theoxide film which coats the atomized particles.

The atomized alloy particles are preferably prepared by melting thealloy of the desired composition and pro jecting it through a suitablydesigned nozzle with the which possess unique strength properties atelevated temperatures. The particles of oxide distributed throughout thebody appear to impart the unusual strength at elevated temperatures. Theproduction of the oxide coated flakes is time consuming and consequentlyexpensive. It has now been found, contrary to previous belief, thatuseful articles can be made from certain types of atomized aluminumalloy powders. As is Well known, the atomization process involvesdisintegrating a stream of molten metal with a jet of gas, such ascompressed air or by mechanical means. Very finely divided particles canbe produced by this process that will pass through a standard Tyler 100mesh screen.

It is an object of this invention to provide articles having a highstrength at elevated temperatures which are made from atomized particlesof an aluminum base alloy containing manganese as the principal addedalloy component.

Another object is to provide such articles which do not require anypreliminary thermal treatment to place them in condition for service atelevated temperatures.

Still another object is to provide an article made from atomizedaluminum-manganese alloy powder that does not depend upon the presenceof oxide particles to impart strength at elevated temperatures.

These and other objects are achieved by atomizing a substantiallyiron-free aluminum base alloy containing not less than 70% by weight ofaluminum and from 1.5 to 15% by weight of manganese as the principaladded alloy component, and subsequently consolidating and working a massof such atomized particles under the influence of heat and pressure. Theresultant articles have a density closely approximating that of thealloy if.

cast; and in the hot worked condition, they have a tensile strength ofnot less than 12,000 p.s.i. and a minimum yield strength of 10,000p.s.i. at 600 F. after a 100-hour exposure. These tensile and yieldstrength values ,are to be compared with those of some conventionalwrought heat treated aluminum base alloys that have been recommended forservice at elevated temperatures. For example, a wrought aluminum basealloy nominally composed of aluminum, 12.2% silicon, 1.1% magnesium,0.9% nickel and 0.9% copper has in the solution heat treated and agehardened condition a tensile strength of only 5,000 p.s.i. and a yieldstrength of 3,000 p.s.i. after exposure at 600 F. for 100 hours. Underthe same exposure conditions a second well-known aluminum base alloynominally consisting of aluminum, 4.5% copper, 1.5% m gnesium and 0.6%manganese, when worked, solution heat treated and age hardened, has atensile strength of 10,000 p.s.i. and a yield strength of 7,500

aid of a compressed gas. The atomizing conditions should be'so adjustedthat none or only a small proportion of the particles are larger thanmesh 'imicrons opening) and that the majority of the particles will passthrough a 200 mesh screen (74 microns open- 20 ing). The particlesproduced in this manner generally have an irregular shape but for themost part are substantially equiaxed in dimensions and have as-caststructure. The aluminum-manganese constituent in the alloy is veryfinely divided as a result of the drastic chill associated with theatomization process. The surfaces of the particles are, of course,oxidized if the atomization has occurred in air or in some otheroxidizing atmosphere, however, the oxide skin is very thin and theamount of oxide introduced into the final product is too small to affectthe properties thereof to any significant extent.

The manganese content of the alloy should be between 1.5 and 15% byweight, as mentioned above, and preferably within the range of 5 to 10%to obtain the highest strength at elevated temperatures. If less than1.5% is employed, the minimum strength is not achieved and if more than15 is present, the worked article has insufiicient ductility and mayfracture under ap lied stresses. Manganese is substantially insoluble inaluminum and whatever small proportion may be dissolved is too small tohave any significant elfect upon the properties of the.

atomized particles. It will therefore be appreciated that the matrix ofthe atomized particles consists of aluminum with a dispersion of finelydivided aluminum-manganese constituent distributed throughout theparticle. The high strength at elevated temperatures appears to becontrolled by the amount of the aluminum-manganese constituent and thefineness of the dispersion.

The alloy may contain the usual impurities associated With aluminum, forexample, silicon and iron. Generally, the silicon impurity should notexceed 0.8% and the iron content should not be more than about 1%. Otherimpurities, such as copper, may also be present in amounts up to 0.5%.In view of the relatively small amount of iron impurity permitted in thealloy, the composition is referred to herein as being substantiallyironfree.

For some purposes, it may be desirable to add one or more elementsselected from the group composed of nickel. cobalt, chromium, titanium,vanadium, zirconium, molybdenum, and tungsten in amounts of 0.1 to 10%each, the total not exceeding 10%. These elements act as hardeners and,like manganese, are substantially insoluble in the aluminum matrix. Toattain the properties attributable to the aluminum-manganeseconstituent, the manganese content of the alloy should exceed the totalamount of any added hardener elements.

To make the Wrought article from the atomized powder, the powder may beinitially formed into a compact that is subsequently worked or it may becharged. directly to a-compression chamber, such as an extrusion presscylinder, and be extruded therefrom after initial consolidation of themass. The initial compact may be made by heatheated to 800 F. andextruded to diameter rod. The Al-15.8% Mn alloy compact was heated to1000 F. before being inserted in the extrusion press in order to improvethe working quality of the compacts. Tensile specimens were cut from theextruded rod and tested without any preliminary thermal treatment, someat room temperature and others at 600 F. after a 100-hour exposure atthat temperature. The composition of the alloys tested and the tensileproperties at both room temejected, cooled, scalped, reheated to the hotworking 10 perature and at 600 F. are given in Table 1 below.

TABLE 1 Tensile properties of extruded AlMn powder products At RoomTemperature At 600 F.

Alloy Percent Mn Tensile Yield Percent Tensile Yield Percent Strength,Strength, Elong. Strength, Strength, Elong.

p.s.i. p.s.i. p.s.i. p.s.i.

A 1.6 29. 900 22, 100 23 12, 400 10, 600 24 B 5.2 37. 900 25, 800 19. 815, 000 12, 800 25. 8 C 10.7 56.100 40. 600 5. 2 20, 400 14, 000 9. D15.8""--- 63, 600 Broke 0 100 18, 100 1. 0 E 6.21 61, 100 42, 200 6. 20,200 14, 400 19. 2 F tgMgi- 44, 400 35,600 1. 5 20, 400 16, 600 2. 2

.5 i. G 4.8 MEI-{ 44, 800 36,200 8. 2 13, 200 10,300 9. 8

temperature and hot worked. In some cases it may be It is apparent fromthe foregoing that the tensile and desirable to reheat the compact totemperatures as high yield strengths of the alloys increase with anincrease as 1150 F. before hot working in order to obtain adequateworkability. This should only be done if more than 3% manganese ispresent. Where the powder is charged to a compression chamber, it may beinitially heated to a temperature between 700 and 900 F. and introducedto the chamber or it may be charged cold and heated within the chamber.Alternatively, it may be heated to an intermediate temperature, thencharged to the chamber and brought to the desired temperature. When thepowder is to be compacted and immediately extruded, it is generallyconvenient to compress the powdered mass against a blind die in a presscylinder and then substitute an extrusion die for it to produce thedesired extruded shape. Although reference has been made to theextrusion of the powder mass, it is to be understood that it can besubjected to other types of hot working operations, such as rolling,forging or pressing, providing a suitable compact is initially produced.The hot working is preferably performed within the temperature range of700 to 900 F.

Our invention is illustrated by the following examples whereinaluminum-manganese atomized powders were consolidated and the producthot worked. The powders were of a fineness such that approximately 75%passed through a 200 mesh screen and substantially all of the remainderpassed through a 100 mesh screen. Each alloy powder was chargedto anextrusion press cylinder preheated to 800 F. and compressed against ablind die under a pressure of 100,000 p.s.i. for a period ofapproximately one minute. In the course of charging and compressing thepowder the temperature of the compact reached 700-800 F. After thecompact wasthus formed it was either ejected from the cylinder, andsubsequently hot worked or it was retained in the cylinder, an extrusiondie having a diameter opening therein substituted for the blind die, andthe compacted mass extruded to forma rod in diameter. Only the compact.of the Al1.6% Mn alloy was extruded directly after formation; thecompacts of the other alloys were ejected from the cylinder, cooled,scalped and reheated for hot working. The compacts of the Al5.2% Mn, Al10.7% Mn, Al6.2% Mn4.9% Ni, Al4.9% Mn- 3.5% Ti, and Al-4.8% Mn4.7% Zralloys were reheated to 850 F., inserted in an extrusion press cylinderin the manganese content. However, the upper limit for useful purposesappears to be 15% since the ductility at 600 F. is so low. The tensileproperties obtained at 600 F. are considerably higher than those of thetwo commercial aluminum base alloys referred to hereinabove. It is alsosignificant that the high strength at 600 F. was obtained without anypreliminary thermal treatment of the worked powder products, such as asolution heat treatment, which is an economic advantage.

Having thus described our invention and certain embodiments thereof, weclaim:

1. A hot worked aluminum base alloy powder article free from aluminumoxide except as an incidental im purity and having a maximum ironcontent of 1%, said hot worked alloy powder article being formed fromatomized powder of an aluminum base alloy containing at least 70% byweight of aluminum and from 1.5 to 15% by weight of manganese as theessential component, the amount of said component exceeding the totalquantity of any hardening elements present in the alloy, said alloybeing substantially free from elements which form a solid solution withaluminum, except as they occur as impurities, said hot worked articlebeing characterized in the as-worked condition by a tensile strength at600 F. after a hour exposure of not less than 12,000 p.s.i. and a yieldstrength of not less than 10,000 p.s.i.

2. A hot worked aluminum base alloy powder article according to claim 1wherein the manganese content is 5 to 10%.

3. A hot worked aluminum base alloy powder article according to claim 1wherein the alloy also contains at least one hardening element selectedfrom the group consisting of nickel, cobalt, chromium, titanium,vanadium, molybdenum, Zirconium and tungsten in amounts of 0.1 to 10%each by weight, the total not exceeding 10% by Weight, the manganesecontent of said alloy exceeding the total amount of hardening elementsadded thereto.

Jones June 23, 1942 Ennor Oct. 15, 1957

1. A HOT WORKED ALUMINUM BASE ALLOY POWDER ARTICLE FREE FROM ALUMINUMOXIDE EXCEPT AS AN INCIDENTAL IMPURITY AND HAVING A MAXIMUM IRON CONTENTOF 1%, SAID HOT WORKED ALLOY POWDER ARTICLE BEING FORMED FROM ATOMIZEDPOWDER OF AN ALUMINUM BASE ALLOY CONTAINING AT LEAST 70% BY WEIGHT OFALUMINUM AND FROM 1.5 TO 15% BY WEIGHT OF MANGANESE AS THE ESSENTIALCOMPONENT, THE AMOUNT OF SAID COMPONENT EXCEEDING THE TOTAL QUANTITY OFANY HARDENING ELEMENTS PRESENT IN THE ALLOY, SAID ALLOY BEINGSUBSTANTIALLY FREE FROM ELEMENTS WHICH FORM A SOLID SOLUTION WITHALUMINUM, EXCEPT AS THEY OCCUR AS IMPURITIES, SAID HOT WORKED ARTICLEBEING CHARACTERIZED IN THE AS-WORKED CONDITION BY A TENSILE STRENGTH AT600* F. AFTER A 100 HOUR EXPOSURE OF NOT LESS THAN 12,000 P.S.I. AND AYIELD STRENGTH OF NOT LESS THAN 10,000 P.S.I.